Obesity is a medical condition affecting more than 30% of the population in the United States. Obesity affects an individual's quality of life and contributes significantly to morbidity and mortality. Surgical procedures have been developed for involuting the gastric cavity wall to reduce stomach volume as a treatment for obesity. In the gastric volume reduction (GVR) procedures (e.g., reduction gastroplasty, gastric plication, greater curvature plication, etc.), multiple pairs of suture anchoring devices, such as T-Tag anchors, are deployed through the gastric cavity wall. Preferably, the suture anchors are deployed through a small diameter port in a minimally invasive surgical procedure to reduce trauma to the patient. Following deployment of the T-Tag anchors, the suture attached to each individual pair of anchors is cinched to approximate the tissue, and secured to involute the cavity wall between the anchors. This procedure is described in greater detail in co-pending U.S. patent application Ser. Nos. 11/779,314 and 11/779,322, which are hereby incorporated herein by reference in their entirety. The GVR procedures described in these applications require individual placement of each suture anchor pair into the cavity wall tissue, and subsequent tensioning of the suture between the anchor pairs in order to involute the tissue.
The individual placement of the T-Tag anchors and manual suture tensioning is time intensive; increasing the duration, complexity and cost of the GVR procedure. To simplify and improve the GVR procedure, and to facilitate other small incision site surgical procedures within the peritoneal cavity, a stapler has been developed having a low-profile for use in small diameter (i.e. 5 mm or less) laparoscopic ports, a single trocar containing multiple small laparoscopic ports, or through a semi-rigid or flexible endoscopic platform (e.g., for use in natural orifice surgical procedures, single site laparoscopy, etc.). FIG. 1 illustrates an exemplary low profile stapler for use in GVR and other small incision site procedures in the peritoneal cavity including but not limited to reinforcement of staple lines (e.g., “oversewing” of a vertical sleeve gastrectomy), closing of surgical defects (e.g., gastrotomy closure), and fixation of temporary (e.g., liver retraction) or permanent (e.g., hernia mesh, gastric band securement) medical devices. As shown in FIG. 1, the stapler 10 includes a handle 12 having a pistol grip 14 shaped for grasping by a surgeon. A trigger assembly 16 is movably coupled to handle 12 to be drawn towards the pistol grip 14 during staple deployment. An elongated staple housing 20 having a longitudinal axis extends distally from handle 12. Housing 20 has sufficient length (on the order of 18″) to enable use within an obese patient at numerous trocar access sites for traditional laparoscopic approaches. Likewise, housing 20 is sized to allow for passage through a small (3-5 mm) diameter trocar, although functional devices of a larger diameter are also possible without departing from the overall scope of the invention. A staple deploying assembly is at least partially disposed within the interior of housing 20 for discharging staples from a distal deployment opening 22. Trigger assembly 16 facilitates both the advancement of staples through housing 20, as well as the deployment of the staples from the distal opening 22
To obtain a large tissue purchase (which is desirable in GVR procedures) while using a small diameter delivery shaft, the stapler 10 deploys fasteners or staples having a folded, closed loop configuration. These closed loop or “box” staples have a small width in the initial, unformed condition. The width of the staple is expanded during opening and forming to allow the staple to obtain a large tissue purchase. FIG. 2 illustrates an exemplary box staple 30 for deployment from stapler 10. Staple 30 comprises a length of wire formed into a crown or back span 32 and first and second leg portions 34, 36 that intersect with opposite ends of the back span. The wire has a cylindrical cross-section, but may have other shapes (e.g., rectangular, elliptical, etc.) to provide optimal strength for the application or to aid in the feeding of the staples, and may or may not be uniform along the length of the wire. Leg portions 34, 36 intersect with back span 32 at an approximate angle α of 90° and extend in a substantially parallel fashion forward of the back span. Opposite back span 32, leg portions 34, 36 are bent inward to form staple end segments 40, 42. In a loop shape, two lengths of wire may be disposed across one side of the shape to enclose the shape, as demonstrated by the end segments 40, 42. Staple legs portions 34, 36 are bent at end segments 40, 42 to make one of the leg portions at least one wire diameter longer in length than the other leg portion. The longer length of one leg portion (i.e. staple leg 34 in FIG. 2) enables the end segments 40, 42 to lie in a common plane with back span 32. The tips of end segments 40, 42 are angled to form sharp prongs 46 for piercing tissue.
In stapler 10, a stack of the staples 30 is fed longitudinally through the housing in a plane parallel to the housing longitudinal axis. Within the staple stack, staples may be spaced apart from other staples, in contact with other staples, or alternate between states of contact and spaced. The staple stack preferably includes a large number of staples to facilitate procedures, such as GVR, which require a large number of tissue appositions or junctions. The staples are individually advanced outside of the open stapler end 22, and expanded open through actuation of the handle. After the staple pierces or otherwise engages the tissue sections to be joined, the stapler draws the expanded staple legs back inward to close the staple through the tissue. Box staples provide a number of advantages over previous surgical staple designs. These advantages include the ability to: use a smaller incision site, construct the staple from a stronger material, increase the work hardening in the formed staple through a greater number of bending points during formation, and feed the staples in a longitudinal rather than a vertical stack. Additional details regarding the closed loop staple design, as well as staple applicators, procedure applications, and methods of use are disclosed in co-pending U.S. patent application Ser. No. 12/359,351 filed Jan. 26, 2009 entitled “A SURGICAL STAPLER FOR APPLYING A LARGE STAPLE THROUGH A SMALL DELIVERY PORT AND A METHOD OF USING THE STAPLER TO SECURE A TISSUE FOLD”, co-pending U.S. patent application Ser. No. 12/359,354 filed Jan. 26, 2009, entitled “A SURGICAL STAPLER FOR APPLYING A LARGE STAPLE THROUGH A SMALL DELIVERY PORT AND A METHOD OF USING THE STAPLER TO SECURE A TISSUE FOLD”, co-pending U.S. patent application Ser. No. 12/359,357 filed Jan. 26, 2009 entitled “A SURGICAL STAPLER FOR APPLYING A LARGE STAPLE THROUGH A SMALL DELIVERY PORT AND A METHOD OF USING THE STAPLER TO SECURE A TISSUE FOLD”, co-pending U.S. patent application Ser. No. 12/608,860 filed Oct. 29, 2009, entitled “BOX STAPLE METHOD WHILE KEEPING SAID BACK SPAN IN SUBSTANTIALLY ITS ORIGINAL SIZE AND SHAPE”, and co-pending U.S. patent application Ser. No. 12/609,336 filed Oct. 30, 2009, entitled “A METHOD FOR APPLYING A SURGICAL STAPLE”, which are hereby incorporated herein by reference in their entirety.
Despite the numerous advantages in using box staples, feeding a large number of the small staples through a relatively long delivery shaft can sometimes result in misalignment of the staples within the stack, causing the staples to jam prior to reaching the open stapler end. Jamming is particularly a concern when the staples are advanced through the delivery shaft by contact between the staples themselves, i.e. a driving force is applied to the end of the stack and transferred through the stack by each staple applying a force against the next previous staple in the stack in order to drive the full stack forward through the shaft. Previous stapler designs have reduced the potential for staple jamming by balancing loads between a number of flexible staple advancing and stopping components. However, this load balancing adds complexity and cost to the stapler.
Accordingly, to facilitate GVR and other procedures involving the fastening of layers of tissue within the peritoneal cavity, it is desirable to have a simplified, cost effective staple feeding mechanism for reliably feeding a large number of staples through a low profile stapler without misalignment and/or jamming of the staples. In particular, it is desirable to have a staple feeding mechanism for a low profile stapler which includes rigid, individual staple advancers for spreading the driving force of the mechanism through out the staple stack. Additionally, it is desirable to have a staple feeding mechanism in which the rigid staple advancers can be moved in and out of engagement with the staple stack during each staple deployment sequence. Doing so through a substantially rigid body motion (translation or rotation) of staple advancing components simplifies the staple feeding process and eases the strength and flexibility requirements for the staple advancing and stopping components by reducing the overall load requirements in the system. Further, it is desirable to have a staple feeding mechanism that advances the staple stack as part of the staple firing sequence without the need for separate actuation. Furthermore, it is desirable to have a staple feeding mechanism in which the staple driving member and controls are located within the staple housing rather than the handle. The present invention provides a staple feeding mechanism for a surgical stapler which achieves these objectives.